Participants were questioned on their level of activity, with people in one survey even wearing a device that measured activity. The subjects also had to answer questions on their perceived levels of physical activity.

Demographic data including gender, age and access to medical care was also recorded.

It was found that participants’ perception of keeping fit often did not match up with their actual activity levels.

The team then viewed death records from 2011 and determined that people who thought of themselves as less active than others were up to 71 per cent more likely to die during the follow-up period than people who thought they were more active than their peers.

“Our findings fall in line with a growing body of research suggesting that our mindsets - in this case, beliefs about how much exercise we are getting relative to others - can play a crucial role in our health,” Dr. Crum commented.

The results have been published in journal Health Psychology, with the authors suggesting the placebo effect could be the reason behind their findings.

“Following this logic, someone who does not believe that she is exercising enough may get fewer physiological benefits from the activity than someone who believes she is exercising enough,” Dr. Crum continued. “Placebo effects are very robust in medicine, it is only logical to expect that they would play a role in shaping the benefits of behavioural health as well.”

She adds that health can worsen in people who perceive they are doing worse than their peers, which can lead to depression, feeling fearful and less physical activity.